Open up Settings and scroll down to Passwords & Accounts, then choose Add Account on the right side of the screen.
For mail service, choose Other at the bottom of the list.
For Account Type, choose Add Mail Account.
In the New Account Window, enter your information in the corresponding fields.
In the final account details window, make sure IMAP is selected for account type. Enter zlight.earlham.edu, your Earlham username and password in both Incoming and Outgoing Settings.